Aboveground Rectangular Secondary Containment Generator Base Tank with Internal Flexible Bladder

ABSTRACT

The present invention is a containment tank or a generator set including an outer tank and an inner flexible tank that offers a storage area for diesel fuel for a diesel engine powered generator set. So that the generator set diesel engine have ready source of clean diesel fuel the inner flexible tank provides a corrosion-free storage area that will not corrode or contaminate the diesel fuel. The outer tank is designed to provide a structure that not only protects the inner tank from damage, but acts as a support structure for the diesel engine generator set and other components (enclosure, switchgear, etc.) that are needed for the generator sets protection from wind, rain or snow or to act as control devices for diesel engine generator set. Also, since the design of the inner tank is flexible, it can be replaced easily through a manway formed on the outer tank without having to disconnect or disassemble the generator set.

FIELD OF THE INVENTION

The present invention relates to storage tanks, and more particularly to storage tanks with redundant containment structures for containing hazardous materials.

BACKGROUND OF THE INVENTION

Storage tanks are used throughout the world for a variety of purposes. One of the more significant uses for tanks of this type is for the containment of fuels for use at the location of the tanks, such as to store diesel fuel for emergency power diesel engine generator sets. With hazardous materials such as fuels, it is necessary to provide certain safeguards for the storage tanks to protect the environment from a tank leak. These safeguards are normally the requirements of the authority having jurisdiction that necessitate these tanks have the capability for secondary containment of any liquid that could leak from the primary or inner tank.

As best shown in FIGS. 1 and 2, an example of a prior art containment tank 10 on which can be mounted a generator 1000, a diesel engine 2000 and a fan 3000 is shown which includes a primary inner tank 12 formed with a lower member 14 and an upper member 16. The lower member 14 is generally rectangular in shape with a bottom wall 18, a number of upwardly extending side walls 20 secured to each side of the bottom wall 18, and one or more support or bracing walls 22 secured to the bottom wall 18 and to opposed side walls 20 at each end. The upper member 16 is affixed to each of the side walls 20 opposite the bottom wall 18 to form an enclosed interior 24 within the inner tank 12. Within the structure of the upper member 16 are included a number of fittings 25 to which various hoses (not shown) can be connected in order to introduce and withdraw fluids from within the inner tank 12. The upper member 16 can also be strengthened by attaching a stiffener 26 to the upper member 16 that extends across the upper member 16 to each of the side walls 20 to be attached thereto and enhance the strength and rigidity of the inner tank 12.

Each of the components of the inner tank 12 are formed from a metal, such as steel, to provide the required integrity and rigidity to the tank 12 and to enable all of the component to be affixed to one another by welding, to attempt to minimize the formation of leaks between the components of the inner tank 12.

The inner tank 12 is dimensioned to be able to fit within a secondary outer tank 28 to form the containment tank 10. The outer tank 28 includes a bottom wall 30 and a number of side walls 32 secured to the bottom wall 30 at one end. The side walls 32 define and enclosure 34 within which the inner tank 12 can be positioned and secured. The inner tank 12 is affixed to the outer tank 28 using an outwardly extending edge 36 of the upper member 16 of the inner tank 12. When the inner tank 12 is positioned within the enclosure 34, the outwardly extending edge 36 rests on each of the side walls 32 of the outer tank 28 and can be secured thereto, such as by welding. This additionally seals the enclosure 34 formed in the outer tank 28, which can retain any fluid escaping from the inner tank 12.

In prior art containment tank constructions, as described above, the primary inner tank is constructed of steel and is welded into a secondary containment or outer tank to form one contiguous tank construction. Thus, in the event of a leak in the primary inner tank which is contained by the secondary outer tank, due to the unitary construction of the containment tank, the entire tank including both the damaged primary inner tank and the undamaged secondary outer needed to be replaced. This results in excessive replacement costs and extended downtime for the particular device connected to the storage tank, such as an emergency power diesel engine generator set.

Additionally, in the applications for prior art storage tanks in containing fuels, such as for providing a local fuel source for stand-alone power generation systems, e.g., generator sets, these systems are used primarily to provide emergency electrical power in the event of a utility electrical power outage. The ability of the stand-alone power generation system to start and take-over as the primary source of electrical power coupled to life safety system within seconds following a utility power outage is paramount to sustaining human life. The performance of these power generation systems is dependent upon having a fuel source in the form of the storage tank that is clean and free of contaminants. However, with the construction of prior art tanks with a steel inner tank, the steel forming the inner tank can oxidize and/or corrode when in storage or over years of operation. This particulate matter formed as a result of the corrosion can contaminate the fuel held within the inner tank, can obstruct fuel filters located in output channels for the fuel dispense from the tank, and/or can clog engine the fuel injection mechanisms of the power generation systems. As a result, the emergency power generator set connected to the storage tank may not be able to start when it is needed during a utility power failure in order to support the critical or life-safety load, which is highly undesirable.

Therefore, it is desirable to develop a storage tank for hazardous materials, such as fuels, having a primary inner tank that is formed of a material capable of reliably holding the hazardous material therein to prevent leaks that resists corrosion and is rugged enough to withstand testing in accordance with the applicable requirements of the code under which they are built (NFPA, etc.). Further, if it should become necessary to replace the primary inner tank due to a leak that has formed in the inner tank, the inner tank should be able to be removed from within the secondary outer tank in a manner that enables the outer tank to be reutilized, to minimize the downtime for the tank and to maximize the operating time for the emergency power source.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a storage tank for a hazardous material is provided that includes an internal flexible bladder forming the inner tank that is contained within a more conventional rigid outer tank. The flexible material forming the inner tank has properties that enable the material to resist degradation of the flexible material over a longer period of time than necessary for the corrosion of a conventional steel inner tank, such that the flexible inner tank provides longer corrosion and contaminant resistance than prior art storage tank constructions.

According to another aspect of the present invention, the flexible inner tank is releasably connected to the outer tank. Therefore, when a leak has formed in the inner tank, the inner tank can be removed from the outer tank and replaced without having to also replace the outer tank. This interchangeability of the inner tank structures within a single outer tank greatly decreases the downtime for a tank that has formed a leak.

According to still another aspect of the present invention, the top of the tank contains one or more openings to which the collar of the flexible inner tank can be attached to the secondary containment outer tank. The collar of the inner tank is attached to the top of the outer tank around the periphery of the opening and the opening itself is covered with a removable manway. The manway permits a person to at least partially enter the inner tank, such as to inspect the interior of the inner tank, and contains fittings therein that permit solid or flexible pipe connections to be attached.

Numerous other features, aspects, and advantages of the present invention will become apparent from the following detailed description taken together with the drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode currently contemplated of practicing the present invention.

In the drawings:

FIG. 1 is an isometric view of a prior art storage tank;

FIG. 2 is an exploded, isometric view of the prior art storage tank of FIG. 1;

FIG. 3 is an isometric view of a storage tank including a flexible inner tank constructed according to the present invention;

FIG. 4 is an exploded, isometric view of the storage tank of FIG. 3;

FIG. 5 is a cross-sectional view along line 5-5 of FIG. 3;

FIG. 6 is a partially broken away circular sectional view along line 6-6 of FIG. 3;

FIG. 7 is a partially broken away circular sectional view along line 7-7 of FIG. 3; and

FIG. 8 is a partially broken away circular sectional view along line 8-8 of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

With reference now to the drawing figures in which like reference numerals designate like parts throughout the disclosure, a containment tank constructed according to the present invention is illustrated generally at 100 in FIG. 3. The tank 100 is constructed similarly to the prior art tank 10 with an inner tank 112 and an outer tank 114. The outer tank 114 that can be utilized in the construction of the container tank 100 can be virtually the same as that used in the prior art tank 10, with a bottom wall 116 and a number of side walls 118 formed from a suitable metal material and secured to one another to form a fluid-tight seal between the respective walls, such as by welding. The side walls 118 each include a central panel 120, a lower flange 122 and an upper flange 124, with the lower flange 122 affixed to the side of the bottom wall 116. The lower flange 122 and the upper flange 124 are joined at each end by an end plate 126, and between the end plates 126 by a number of spaced pairs of support gussets 128. Each pair of gussets 128 are joined by a mounting plate 130 including an aperture 132 therein that is used as an attachment point for the lifting of the tank 100 and any generator system components mounted thereto. Adjacent, and preferably between the pairs of gussets 128, the upper flange 124 also includes openings 134 to be utilized in securing the generator system components to the tank 100. Due to the reinforced construction for the side walls 118, these mounting openings 134 for attaching the generator system components, such as a generator 1000, a diesel engine 2000 and a fan 3000 or, in some cases, an enclosure (not shown) to the outer member 114 can support a minimum of five thousand (5,000) lbs per mounting location to directly support the generator system components.

At one end of the bottom wall116, the side wall 118 are joined by an end wall 136 that is secured to the bottom wall 16 and to each of the side walls 118 in a manner to provide a fluid-tight seal between the end wall 136 and each of the bottom wall 116 and the side walls 118. The end wall 136 also has an inwardly extending flange 138 disposed slightly below, but parallel with and between the upper flanges 124 of each side wall 118. The end wall 136 may also have certain fittings 140 disposed therein or attached thereto, such as an emergency vent or vent fitting.

Generally opposite the end wall 136, but spaced inwardly from the opposite end of the bottom wall 116, a second end wall 142 is positioned and secured to the bottom wall 116 and the side walls 118. The end wall 142 is formed similarly to the end wall 138 with an inwardly extending flange 144, and is secured to the bottom wall 116 and the side walls 118 in a similar manner to provide a fluid-tight seal therebetween, and to effectively create an enclosure 146 between the bottom wall 116, the side walls 118 and the end walls 138 and 142. The enclosure 146 may also have a number of different elements positioned therein, such as one or more internal boxed segments 148 and 150 that provide areas that are open to the enclosure 146 of the outer tank 114 to maintain spatial separation for a leak detection switch (not shown). These structures 148 and/or 150 allow any build-up of internal pressures within the enclosure 146 of the outer tank 114 to escape through the emergency vent (not shown) located within the fitting 140 within the end wall 138.

An enclosure wall 151 is secured to the bottom wall 116 and between the side walls 118 a distance from the end wall 142 to form a space 153 between the enclosure wall 151 and the end wall 142. This space 153 formed therein can receive various components (not shown) that are used to operate the generator system components to be secured to the tank 110. The wall 151 is preferably secured to the side walls 118 by suitable fasteners 155 so that the wall 151 can be removed if necessary to access the space 153 without having to remove any of the generator system components from the tank 110.

Looking now at FIGS. 3-7, the enclosure 146 formed by the walls 116, 118, 138 and 142 is covered by an upper wall 152 formed from a metal material, such as steel. The upper wall 152 is affixed in a fluid-tight manner to each of the flanges 138 and 144 on the end walls 138 and 142, respectively, and to the side walls 118 at a point below the upper flanges 124, to position the upper wall 152 generally coplanar with the flanges 124. The upper wall 152 can include various fittings 154 and 156 (FIGS. 3 and 8) for holding different devices, such as leak detection units and emergency vents (not shown) similarly to the fitting 140 in the end wall 138. The upper wall 152 can also include a stiffening support 158 secured to the underside thereof to enhance the structural integrity of the outer tank 114.

As best shown in FIGS. 4-6, the upper wall 152 also includes an access aperture 160 therein. The aperture 160 provides a means for access into the enclosure 146 of the outer tank 114, and can be covered by a plate 162 that is releasably secured thereto. The plate 162 is formed of a metal material similar to the upper wall 152, and includes a number of openings 164 that can receive suitable fasteners 166 therethrough. The fasteners 166 extend through aligned apertures 168 in the upper wall 152 located around the access aperture 160. The fasteners 166 are held within the openings 164 and apertures 168 by nuts 170 attached to the exposed ends of each of the fasteners 166.

Additionally, the cover plate 162 includes a number of fitting apertures 172 formed therein that provide a connection points for supply and return of fluid into and out of the tank 100, such as diesel fuel, and for other devices, such as an emergency vent, a fuel fill, a fuel level gauge, an atmospheric vent, an engine fuel return/supply dip tubes, and a fuel level switch, among others.

The inner tank 112, as best shown in FIGS. 4 and 5, is a unitary structure formed of a flexible and corrosion-resistant material, such as a suitable polymeric resin. The inner tank 112 includes a single opening 174 formed therein around which is formed a peripheral rim 176 that can be integrally formed with the inner tank 112, or separately formed and secured thereto. The rim 176 has an inner diameter slightly less than that of the access aperture 160, and an outer diameter that is greater than the access aperture 160, such the rim 176 can be engaged around the aperture 160, as best shown in FIG. 5. To hold the rim 176 in this position, the rim 176 includes apertures 178 formed therein that are aligned with the openings 164 in the cover plate 162 and the apertures 168 in the upper wall 152 to receive the fasteners 166 therein. Thus, the fasteners 166 extend through the upper wall 152, the rim 176 and the cover plate 162 to enclose the opening 174 into the inner tank 112, as well as the access aperture 160 into the outer tank 114. Further, due to the compressible and flexible nature of the material forming the rim 176, the compression of the rim 176 between the upper wall 152 and the cover plate 162 effectively seals both the inner tank 112 and the outer tank 114 from the outside environment.

The inner tank 112 is preferably integrally formed with the rim 176, but can be formed of a separately of a different material that is securely attached to the tank 112 in any suitable manner, such as by bonding or any other suitable means. The tank 112 extends inwardly from the rim 176 through the aperture 160 and into the enclosure defined by the outer tank 114. The inner tank 112 is dimensioned to generally conform to the interior of the outer tank 114, such that when filled with a material, such as a fuel, the inner tank 112 unfolds to contact and conform to the shape of the outer tank 114, filling the enclosure 146. Further, the inner tank 112 can be formed of a material than can expand or stretch to conform to the shape of the outer tank 114, while retaining sufficient strength to prevent any leaks in the inner tank 112.

To achieve a UL Listing the inner tank 112 must undergo a hydrostatic pressure test whereby the inner tank 112 is completely filled with water and all air is expelled from the inner tank 112. Then air pressure is gradually applied to the inner tank 112 in five (5) psi increments at a rate not to exceed two (2) psi per minute. The pressure is held for two (2) minutes after each five (5) psi increment until the test gauge pressure of fifteen (15) psi is reached or twenty-five (25) psi for a ULC listing.

With this construction, should a leak develop in the inner tank 112 that is detected by a suitable device secured within the tank 110, after the inner tank 112 is emptied of the material contained therein, the cover plate 162 can be removed to detach the rim 176 from the upper wall 152. With the rim 176 detached, the rim 176 can be drawn away from the outer tank 114 to remove the inner tank 112 from within the enclosure of the outer tank 114. The flexible material forming the inner tank 112 can be compressed, bent or folded to be removed through the access opening 160, allowing the damaged inner tank 112 to be completely removed from within the outer tank 114 without affecting the structure of the outer tank 114. Once removed, a new inner tank 112 can be inserted into the outer tank 114 through the access opening 160 and expanded to return the tank 110 to normal operation.

In some alternative embodiments, multiple inner tanks 112 can be affixed to the rim 176, with each tank 112 being positioned within the enclosure 164 and having an opening (not shown) through which the material can be introduced into the inner tank 112.

Various alternatives are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention. 

1. A material containment tank comprising: a) an outer tank including a bottom wall, a pair of opposed side walls connected to the bottom wall, a pair of opposed end walls each connected to the bottom wall and between the side walls, one end wall spaced inwardly from one end of the bottom wall, and a top wall connected to each of the pair of side walls and the pair of end walls, the top wall defining an access opening therein; b) at least one generator system component attachment assembly located on at least one of the side walls, the at least one attachment assembly adapted to provide an attachment point for a generator system component to the tank; and c) a inner tank disposed within the outer tank, the inner tank formed of a flexible and collapsible material.
 2. The tank of claim 1 wherein the inner tank includes a rim releasably secured to an outer surface of the top wall
 3. The tank of claim 2 further comprising a cover plate releasably secured to the top wall over the rim.
 4. The tank of claim 3 further comprising a number of fasteners affixing the cover plate to the top wall over the rim.
 5. The tank of claim 4 wherein the rim is compressed between the cover plate and the top wall to form a fluid-tight seal.
 6. The tank of claim 3 wherein the cover plate includes at least one fitting therein.
 7. The tank of claim 2 wherein the rim is integrally formed with the inner tank.
 8. The tank of claim 1 further comprising at least one support member secured to at least one of the pair of side walls.
 9. The tank of claim 8 wherein the at least one support member includes a lifting opening formed therein.
 10. The tank of claim 1 further comprising a removable end plate secured between the end walls and spaced from the end wall spaced inwardly from the end of the bottom wall.
 11. A generator set comprising: a) a containment tank including an outer tank including a bottom wall, a pair of opposed side walls connected to the bottom wall, a pair of opposed end walls each connected to the bottom wall and between the side walls, one end wall spaced inwardly from one end of the bottom wall, and a top wall connected to each of the pair of side walls and the pair of end walls, the top wall defining an access opening therein, at least one generator system component attachment assembly located on at least one of the side walls, the at least one attachment assembly adapted to provide an attachment point for a generator system component to the tank; and a inner tank disposed within the outer tank, the inner tank formed of a flexible and collapsible material; and b) at least one generator system component secured to the at least one attachment assembly.
 12. The generator set of claim 11 wherein the inner tank includes a rim releasably secured to an outer surface of the top wall
 13. The generator set of claim 12 further comprising a cover plate releasably secured to the top wall over the rim.
 14. The generator set of claim 13 further comprising a number of fasteners affixing the cover plate to the top wall over the rim.
 15. The generator set of claim 14 wherein the rim is compressed between the cover plate and the top wall to form a fluid-tight seal.
 16. The generator set of claim 13 wherein the cover plate includes at least one fitting therein.
 17. The generator set of claim 12 wherein the rim is integrally formed with the inner tank.
 18. The generator set of claim 11 further comprising at least one support member secured to at least one of the pair of side walls.
 19. The generator set of claim 18 wherein the at least one support member includes a lifting opening formed therein.
 20. The generator set of claim 20 further comprising a removable end plate secured between the end walls and spaced from the end wall spaced inwardly from the end of the bottom wall. 